Three-dimensional (3D) printing refers to a way of forming a stereoscopic object, as compared with the conventional two-dimensional (2D) (i.e., planar) printing technique to draw an image on the surface of a paper or an object. In 3D printing, an object is fabricated by printing an ink serving as a raw material for constituting the object in a desired shape through computer-aided design (CAD). 3D printing is primarily used for prompt preparation of prototypes in order to curtail time and expenses required for the preparation of such prototypes. Therefore, 3D printing can be employed in various areas such as personal products, medical products, automobile parts, construction products, or the like.
3D printing may be classified into a laser-based method such as stereolithography (SLA), selective laser sintering (SLS), and UV inkjet mode, and a non-laser-based method such as transit development plan (TDP), fused deposition modeling (FDM), etc.
3D printing materials used in manufacturing an object by the 3D printing technique are diverse and may include, for example, thermoplastic plastics, metals, paper, nylon, rubber, resins, wood, sand, ceramics, or the like. FDM is the most widely used 3D printing method wherein a thermoplastic resin is melted and extruded to form an object. Raw materials commonly used in the FDM method may include, for example, acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), or the like.
As one of the major materials, ABS is an engineering plastic having good mechanical properties such as toughness and may be applicable in various ways in the 3D printing field. However, it involves disadvantages that it has high melting temperatures, suffers deformation (e.g., shrinkage) in shape during a process, and generates noxious gas; hence, it is not proper for working in an office or a studio.
Recently, PLA resins have attracted attention as a 3D printing material since they are not toxic when they are processed, have relatively low melting temperatures that allow low-temperature processing, and are derived from biomass materials such that final products are also eco-friendly biodegradable. Further, the PLA resins less shrink than olefin resins when they are cooled, and are transparent as well as readily dyed. Despite the above advantages, they are slowly solidified and prone to heat deformation due to low glass transition temperatures (Tg) and low crystallinities. Since they have an elongation of about 5% or less, they are poorly flexible and are prone to breakage. Further, the PLA resins may have insufficient mechanical properties such as impact strength and toughness. In order to overcome such shortcomings as described above, the PLA resins may need to be modified as desired.
It has been attempted to render the conventional PLA resins flexible by adding thereto a plasticizer or a chain extender or by further blending a rubbery component therewith, and to reinforce such physical properties as impact strength and toughness of the conventional PLA resins by adding various reinforcing agents thereto (see Chinese Patent Laid-Open Publication Nos. 103146164, 103467950, and 103087489). However, there is still a need for further improving the solidification rates of PLA resins required when they are processed and the flexibility of final products.
The present inventors have studied to provide a polylactic acid resin composition useful for 3D printing, with improved flexibility and thermal characteristics. As a result, a PLA resin copolymerized with a flexible component has been provided.